Home composting transforms your organic waste into a valuable amendment for your garden. Discover all the keys to producing your own professional-quality compost and naturally enriching your soil without spending a penny.
Compost: the gardener's black gold
Homemade compost is much more than just waste recycling. It's a living ecosystem that produces one of the best organic amendments for your garden. Rich in humus, beneficial microorganisms, and assimilable nutrients, compost sustainably improves soil structure and nourishes your plants naturally.
Every French household produces an average of 200 kg of organic waste per year, including 80 kg of kitchen waste. Instead of throwing it away, composting transforms it into a fertile resource while reducing your trash by 30 to 40%. This ecological and economical approach fits perfectly into a sustainable gardening strategy.
Combined with Fertilaine fertilizers, your homemade compost creates a complete fertilization program that meets all your garden's needs throughout the year.
Understanding the composting process
Composting is a natural aerobic decomposition process orchestrated by billions of microorganisms. Understanding this mechanism allows you to optimize your production and obtain high-quality compost.
The actors of decomposition
Compost teems with invisible and visible life working to transform organic matter:
- Bacteria: primary actors, they break down simple molecules and generate the characteristic heat of active compost.
- Fungi: specialized in degrading woody and cellulosic materials.
- Actinomycetes: these filamentous bacteria decompose resistant materials and give mature compost its forest floor smell.
- Compost worms: true transformation factories, they digest matter and produce exceptional vermicompost.
- Arthropods: sowbugs, millipedes, and mites fragment debris and aerate the compost.
The phases of composting
Compost goes through several stages before full maturation:
- Initial mesophilic phase (1-3 days)
Mesophilic bacteria colonize fresh waste. The temperature gradually rises to 40°C. This phase requires a good balance between nitrogenous and carbonaceous materials.
- Thermophilic phase (1-2 weeks)
The temperature reaches 50 to 70°C. Thermophilic bacteria destroy pathogens, weed seeds, and rapidly decompose organic matter. This temperature increase indicates well-balanced compost.
- Cooling phase (2-4 weeks)
The temperature gradually drops. Fungi and actinomycetes take over to degrade complex compounds. The compost takes on a brownish hue.
- Maturation phase (2-6 months)
The compost cools completely. Worms and microfauna complete the transformation. Stable humus forms, giving the compost its dark brown color and undergrowth smell. It is at this stage that it becomes an optimal quality amendment.
Choosing and installing your composter
The choice of composting system depends on your available space, the volume of waste produced, and your commitment.
Wood or plastic composter
A classic solution for gardens, a closed composter protects the process from bad weather and pests:
- Recommended volume: minimum 300 liters for a family of 4.
- Ideal location: semi-shade, on bare ground to facilitate colonization by soil organisms.
- Materials: untreated wood or recycled plastic, with a lid and access hatch.
- Advantages: protection against animals, moisture retention, neat appearance.
Compost heap
A traditional and economical method, the compost heap is suitable for large gardens producing a lot of plant waste:
- Minimum dimensions: 1m x 1m x 1m to reach the critical mass needed for temperature rise.
- Installation: directly on the ground, possibly delimited by pallets or fencing.
- Advantages: large capacity, easy access, optimal natural colonization.
- Disadvantages: exposure to weather, less neat appearance, accessibility to animals.
Apartment vermicomposter
For small spaces, vermicomposting offers a compact and odorless solution:
- Capacity: 40 to 60 liters are sufficient for a couple.
- Location: indoors (kitchen, balcony, cellar) at a stable temperature of 15-25°C.
- Production: compost and liquid compost tea, a concentrated fertilizer.
- Special feature: requires specific worms (Eisenia fetida or andrei).
Rotary composter
A modern solution to speed up the process thanks to easy mixing:
- Composting time: 4 to 8 weeks compared to 6 to 12 months in a classic composter.
- Ergonomics: simple rotation without effort.
- Hygiene: closed system ideal for urban areas.
- Investment: more expensive but significant time saving.
What to compost? The golden rule of organic waste
The quality of your compost depends directly on what you put into it. Not all organic waste is suitable for home composting.
Green materials: the nitrogen of compost
Rich in nitrogen and moist, green materials activate decomposition and nourish microorganisms:
✓ Compost without moderation
- Fruit and vegetable peelings: primary source in the kitchen.
- Coffee grounds with filter: excellent nitrogen-rich activator.
- Tea bags: without metal staples.
- Grass clippings: in thin layers (2-3 cm) to prevent compaction.
- Wilted green plants: tender stems and fresh foliage.
- Cooked vegetable leftovers: plain, without sauce or fat.
- Fresh manure: from chickens, rabbits, horses (excellent activator).
Brown materials: the structuring carbon
Rich in carbon and dry, brown materials structure the compost and absorb excess moisture:
✓ Essential for balance
- Dead leaves: ideally shredded, excellent balancer.
- Straw and hay: provide structure and aeration.
- Unprinted brown cardboard: cut into pieces, absorbs moisture.
- Newspaper: in moderate quantity, crumpled to prevent compaction.
- Sawdust and wood shavings: untreated, in small quantities.
- Twigs and small branches: shredded to accelerate decomposition.
- Crushed eggshells: provide calcium and structure.
Waste to absolutely avoid
Some waste disrupts composting or creates nuisances:
✗ Never compost
- Meats and fish: attract pests and release foul odors.
- Dairy products: anaerobic fermentation and unpleasant odors.
- Fats and oils: waterproof the compost and slow down decomposition.
- Carnivore droppings: health risks (dogs, cats).
- Diseased plants: risk of pathogen spread.
- Weeds gone to seed: will reseed in your garden.
- Treated or varnished wood: toxic chemicals.
- Charcoal ashes: heavy metals and toxic substances.
- Animal litter: even biodegradable, health risks.
Waste to compost with caution
Some materials require special precautions:
- Citrus fruits: in small quantities, their acidity can slow down the process.
- Onions and garlic: moderately, they can repel worms.
- Bread and pasta: only in small quantities, attract rodents.
- Wood ashes: sprinkle lightly, rich in potash but alkalizing.
- Thuja and conifer trimmings: in very small quantities, slow down decomposition.
The perfect balance: the carbon/nitrogen ratio
The secret to successful compost lies in the balance between green materials (nitrogen) and brown materials (carbon). This optimal ratio is around 25-30 volumes of carbon to 1 volume of nitrogen.
Recognizing imbalances
Excess nitrogen (too much green)
Symptoms:
- Ammonia or putrefaction odor.
- Viscous and compacted appearance.
- Presence of flies and gnats.
- Blackish liquid runoff.
Solution: Immediately add brown materials (dead leaves, cardboard, straw) and turn to aerate.
Excess carbon (too much brown)
Symptoms:
- Very slow or stagnant decomposition.
- Dry and dusty compost.
- Lack of heat.
- Little visible biological activity.
Solution: Incorporate fresh green materials (grass clippings, peelings) and moisten if necessary.
The alternate layering method
To maintain balance naturally, adopt the mille-feuille technique:
- Start with a draining layer of twigs (10 cm).
- Alternate green layers (5-7 cm) and brown layers (7-10 cm).
- Always finish with a protective brown layer.
- Lightly water dry layers when adding.
This stratification promotes air circulation, regulates moisture, and ensures harmonious decomposition of the whole.
Essential practices for quality compost
Beyond material selection, a few regular actions ensure the success of your composting.
Aeration: oxygenate to accelerate
Composting is an aerobic process that requires oxygen. A well-aerated compost decomposes 3 to 4 times faster than compacted compost:
- Frequency: turn every 2-3 weeks during the active phase.
- Technique: mix layers from the center outwards with a pitchfork or compost aerator.
- Benefits: homogenization, reactivation of microbial activity, elimination of anaerobic pockets.
- Alternative: incorporate structuring materials (twigs, straw) that create natural aeration channels.
Moisture: neither too much nor too little
The ideal moisture content of compost is around 50-60%, similar to a wrung-out sponge:
Sponge test
Squeeze a handful of compost in your hand:
- Perfect moisture: a few drops pearl, compost retains its shape.
- Too dry: no drops, compost crumbles → water lightly.
- Too wet: water flows abundantly → add absorbent brown materials.
Temperature monitoring
Temperature reveals the activity of your compost:
- 20-30°C: starting phase or maturing compost.
- 40-60°C: optimal active phase, excellent decomposition.
- 60-70°C: thermophilic phase, hygienization of compost.
- Above 70°C: overheating, risk of destroying beneficial microorganisms → aerate.
A compost thermometer allows you to precisely track these variations and intervene at the right time.
Shredding: accelerating decomposition
The more fragmented the waste, the larger the surface area for microorganisms to act upon:
- Coarse shredding: cut large vegetables, section stems.
- Fine shredding: use a shredder for branches and trimmings.
- Time saving: divides composting time by 2 to 3.
- Structural improvement: more homogeneous mixing and better aeration.
Solving common composting problems
Even with good practices, some inconveniences can arise. Here's how to identify and correct them.
Bad odors
Possible causes:
- Excess nitrogenous materials (kitchen waste).
- Lack of oxygen (compacted compost).
- Excess moisture creating anaerobic zones.
Immediate solutions:
- Generously incorporate brown materials (leaves, cardboard).
- Turn vigorously to reoxygenate.
- Add a layer of garden soil or mature compost to absorb odors.
- Systematically cover kitchen contributions with carbonaceous materials.
Presence of flies and gnats
Causes: Exposed kitchen waste, excess moisture.
Solutions:
- Bury fresh waste in the center of the compost.
- Immediately cover with 5-10 cm of brown materials.
- Install an airtight lid on the composter.
- Avoid large quantities of citrus and onions (attract drosophilas).
Compost too dry that doesn't decompose
Causes: Sun exposure, excess brown materials, lack of nitrogen.
Solutions:
- Water regularly during dry weather (like a plant).
- Move the composter to partial shade.
- Add nitrogen-rich green materials (grass clippings, peelings).
- Incorporate an activator: nettle manure, fresh manure or Fertilaine amendment
Rodents and undesirable animals
Prevention:
- Never compost meats, fish, dairy products.
- Use a closed composter with rodent-proof mesh at the bottom.
- Bury food scraps deep.
- Keep the compost active and warm (rodents avoid compost at 50°C+).
Proliferation of white fungi
Diagnosis: Positive sign! These mycelia indicate active decomposition, particularly of woody materials.
Action: No intervention necessary. The fungi will disappear naturally during the maturation phase.
When and how to use your compost?
Knowing how to recognize mature compost and using it at the right time maximizes its benefits for your garden.
Recognizing mature compost
Ready-to-use compost has the following characteristics:
- Appearance: homogeneous texture, dark brown to black color
- Odor: pleasant scent of undergrowth and humus
- Structure: friable and crumbly, like potting soil
- Temperature: identical to ambient air (no residual heat)
- Initial materials: unrecognizable, only a few woody pieces remain
- Germination test: cress seeds germinate normally in pure compost
Young compost: a spring booster
Compost that is 3-4 months old and not fully decomposed can be used advantageously:
- Fertilizing mulch: spread on the surface (5-10 cm) in vegetable gardens and orchards
- Optimal period: autumn and winter, final decomposition will occur in the soil
- Benefits: progressive nutrient supply and winter protection
- Precaution: do not incorporate directly into seedlings, risk of nitrogen starvation blockage
Mature compost: universal amendment
After 6-12 months of maturation, compost becomes a complete amendment:
In the vegetable garden
- Soil preparation: incorporate 3-5 kg/m² before planting
- Surface application: nutritious mulch of 2-3 cm between rows
- Heavy feeders: tomatoes, squash, cabbage appreciate 5-8 kg/m²
- When transplanting: 1-2 handfuls at the bottom of the planting hole
For the lawn
- Top-dressing: sift and spread 1-2 kg/m² in spring or autumn
- Renovation: 5-10 kg/m² during a complete overseeding
- Frequency: one annual application is sufficient
Flowerbeds and shrubs
- Planting: mix 30-50% compost with excavated soil
- Annual maintenance: lightly fork 2-3 cm of compost onto the surface in spring
- Roses and perennials: particularly responsive to an autumn application
Potted plants
- Potting mix substrate: 20-30% compost mixed with potting soil
- Top-dressing: replace the top 2-3 cm with fresh compost
- Caution: never use pure compost in pots, it's too rich and compact
Compost tea: liquid fertilizer
Infusing compost produces a liquid fertilizer rich in soluble nutrients and microorganisms:
- Fill a cloth bag with mature compost
- Soak in 10 liters of rainwater for 24-48 hours
- Stir regularly to oxygenate
- Dilute 1/10 before use
- Apply by watering or foliar spraying
This "tea" activates soil microbial life and boosts plant growth, particularly effective at the start of cultivation.
Composting according to the seasons
Composting adapts to the natural rhythms of the garden. Each season brings its share of specific materials.
Spring: the restart
- Available materials: first mowings, hedge trimmings, abundant kitchen waste
- Actions: aerate winter compost, transfer mature compost, start a new pile
- Use: spread mature compost before spring plantings
- Tip: spring mowings